Antistatic yarn

ABSTRACT

There is disclosed a method and apparatus for producing yarn having discontinuous staple lengths of metal filaments uniformly interspersed therein by preventing slubbing of the metal multifilament tow during drawing thereof.

United States Patent 1191 Goodbar et a1.

1451 Aug. 13, 1974 ANTISTATIC YARN Inventors: Reid C. Goodbar; Arther Mitchell Pressley, both of Ware Shoals, S.C.

Assignee: Riegel Textile Corporation, Ware Shoals, S.C.

Filed: July 31, 1972 Appl. No.: 276,890

Related US. Application Data Division of Ser. No. 63,755, Aug. 14, 1970, Pat. No. 3,703,073.

us. 01. 57/140 BY, 57/l57AS, 139/425 Int. Cl. D02g 3/12 Field of Search 57/140'12, 140 BY, 157 AS;

References Cited 1 UNITED STATES PATENTS 10/1964 Arthur et a1 57/140 BY 3,288,175 11/1966 Valko 57/140 BY 3,582,445 6/1971 Okuhashi 57/140 BY X 3,582,448 6/1971 Okuhashi et a1, 57/140 BY X 3,586,597 6/1971 Okuhashi 57/157 AS X 3,611,700 10/1971 Vivien 57/140 BY X 3,670,485 6/1972 Brown et a1. 57/140 BY X 3,690,057 9/1972 Norris 57/157 AS X 3,699,590 10/1972 Webber et a1. 57/157 AS X Primary Examiner-Donald E. Watkins Attorney, Agent, or Firm-Pennie & Edmonds ABSTRACT There is disclosed a method and apparatus for producing yarn having discontinuous staple lengths of metal filaments uniform1y interspersed therein by preventing slubbing of the metal multifilament tow during drawing thereof.

9 Claims, 7 Drawing Figures PATENTED AUG 1 31914 SHEET 2 [IF 4 PMENTED AUG 1 31974 SHEET 3 OF 4 Pmmmwm m 3.8%8543 SHEET '4- UP 4 FIG. 5 34? fi L HIIIHI. f Hull 35A i \Jl FIG. 6 L33 ANTISTATIC YARN This is a division, of U.S. Pat. application Ser. No. 063,755, filed Aug. 14, I970 now U.S. Pat. No. 3,703,073.

BACKGROUND OF THE INVENTION In recent years yarns have been developed which when woven into clothing tend to prevent or dissipate electrostatic charges. Such charges are generally the result of friction between fabrics and can be a source of danger or discomfort upon discharge by sparking. It is important for example to prevent electrical discharges in the form of sparks in a hospital operating environment where oxygen in the presence of highly flammable materials is used or when explosive or flammable anesthetic gases are being administered. Computer installations are particularly susceptible to the introduction of error signals caused by static discharge. Certain chemical and other processes must be protected from static discharge through sparking. Other obvious examples of situations which should be kept free from static discharges through sparking are explosive handling and fuel handling.

Various textile yarns have been proposed which incorporate a small quantity of metal filament, usually a stainless steel, which runs as a continuous strand throughout a-yarn or is interspersed in short staple lengths therein. In either case the conduction of incipient electrostatic charges is expected along such yarns to some point where the charge is dissipated or bled off to ground. One of the problems associated with the production of yarns containing staple lengths of metal filament has been the occurrence of slubbing. Slubs are a group or bundle of metal filaments caused by incomplete separation of the metal filaments of a breaker-drawn multifilament tow. Each metal tow may contain for example, 300 filaments of 8 microns diameter each and during drawing of the metal tow, slubs have resulted frequently when the initial set of draw rolls out through the whole of the metal tow instead of causing a gradual attenuation. Such slubs never draw out thereafter notwithstanding several subsequent drawing operations. The final result is nonuniform and poor distribution of the metal filaments throughout the yarn and highly visible grey streaks which will appear in the finished product.

The present invention is concerned with an improved technique for distributing staple lengths of metal filaments throughoutyarns more uniformly to a) improve the anti-static effect and b) enhance the uniformity and appearance of the product. It is believed that the short staple lengths of metal interspersed uniformly as they are, when charged cause local ionization of the adjacent air and a consequent "bleeding off or neutralization of static charges without depending upon conduction of the charge to ground.

SUMMARY OF THE INVENTION In accordance with the present invention a method and apparatus have been devised for drawing a combi nation yarn consisting of textile fiber and metallic filament. Broadly, the method comprises the simultaneous drawing of a textile fiber sliver and a metal filament tow while controlling the tension forces upon the metal filaments in the tow such that gradual breaking of filaments in the tow occurs and the filaments are distributed evenly in staple lengths throughout the textile fiher. In accordance with the invention, as the metal filaments are drawn, they are subjected to the action of draw rolls in a manner to cushion the engagement of the rolls therewith while controlling the tension forces upon the metal filament tow, thereby breaking the filaments at different points between the first two sets of draw rolls. More specifically the method employs feeding the textile fiber sliver into a first set of draw rolls while simultaneously feeding a metal filament tow thereto which is guided into continuous contact with the textile fiber tow.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 and 2 illustrate in plan view a typical draw frame for carrying out the method of the present invention;

FIG. 3 is a vertical cross-section taken in the direction of arrows 33 of FIG. 1;

FIG. 4 is a cross-section taken in the direction of arrows 4'-4 of FIG. 3;

FIG. 5 is a cross-section taken in the direction of arrows 5--5 of FIG. 1;

FIG. 6 is a plan view illustrating the even distribution of metal filament due to the drawing action from respective draw rolls; and

FIG. 7 is a schematic illustration of a woven fabric showing a typical distribution of metal filaments in the warp and filing directions produced by the present invention.

DESCRIPTION OF A PARTICULAR EMBODIMENT Referring to the drawing, a draw frame 10 modified in accordance with the principles of the present invention has been illustrated. As shown in FIG. 1, the draw frame 10 includes sets of four, paired draw rolls 11 comprising individual rolls 12-15. These are journaled in bearings for rotation in frame members 16 and 17. Rolls 12-15 are driven in the conventional manner by means (not shown). Rolls 13 are driven slightly faster than rolls 12, rolls 14 faster than 13 and so on to attenuate the sliver as it passes through the sets of rolls. Furthermore, as is conventional, rolls 13 will have a greater number of teeth than rolls 12, 14 a greater number than 13 and rolls 15 the greatest number of teeth. The separation on centers for example between rolls 12 and 13 in a particular embodiment will be I %inches, 1 inches will separate rolls 13 and 14 and l /8 inches will separate rolls 14 and 15. After passing through the sets of rolls 11, the several slivers (and as will be further described, metal multifilaments dispersed throughout certain slivers) are gathered and enter bin 18 through tube 19. At this point the respective slivers including those having metal multifilaments have been mixed or blended into a single sliver. Another successive drawing or drawings will then follow until fiber attenuation, orientation and further mixing or blending is completed. It will be understood that the apparatus thus far described is conventional.

In the draw frame' 10, two sets of rolls 11 will be mounted side by side, each set being adapted to receive 8 slivers comprising for example three slivers of cotton and five of polyester fiber. For purposes of clarity, only one set of rolls 11 has been illustrated and only five slivers are shown being fed into the draw rolls. The slivers may be individually designated by reference numerals 20-24 with the cotton slivers designated by reference numerals 21 and 22 and the remainder polyester slivers. Each sliver is guided as itis being fed into the draw rolls by a rearward set of spoons 20a-24a and a forward set 20b-24b corresponding to slivers 20-24. Spools 26 and 27 contain a quantity of stainless steel in the form of tows 28, 29. These may be, for example, an austenitic stainless steel (essentially highgrade 18/8 chrome, nickel alloy) such as Brunsmet-304 which is an 8 micron 300 filament tow marketed by Brunswick Corporation Technical Products Div., Chicago, Ill. By way of example but without limitation, the invention contemplates the use of such filaments in the 4-12 micron range.

The tows 28 and 29 first pass from the spools past cut off switches 30, 31 whose arms 30a, 31a sense the presence of each tow 28 and 29. It is the function of the switches 30, 31 to cause the operation of draw rolls 12-15 to cease whenever a break in either of tows 28 and 29 occurs. The stainless steel tows 28 and 29 are fed through guides 32 (FIG. which are mounted to laterally adjustable bracket members 33 secured to frame member 34 by angles 35. The purpose of guides 32 is to assure the precise positioning of each tow 28, 29 such that these will be fed directly upon underlying tows 21 and 22. Lateral adjustment permitted by the elongated slot 33a in bracket 33 will allow the precise adjustment of this relationship.

As the tows 28, 29 proceed through rolls 12l5, the stainless steel filaments will break and gradually be drawn together with cotton slivers 21 and 22. Since the slivers 21 and 22 lie underneath stainless steel tows 28, 29, the cotton fibers will act to cushion the engaging effect of the rolls upon the steel filaments such that the rolls will not cut through the steel tow. Rather, as best seen in FIG. 6, the tows 28 and 29 will be subjected to a gradual attenuation due to the controlled tension placed thereupon by the engagement of adjacent rolls [2 through 15.'Thus, very few breaks will occur at the engaging points of the rolls themselves but rather gradual breakage due to the cushioning action occurs primarily between the respective draw rolls. Because the engaging rolls encounter constantly varying amounts of the steel filmanents in combination with varying amounts of textile fiber, which variation helps to prevent a build-up of tension forces at any particular point, the breaking process occurs only a few filaments at a time. As a result, slubs (relatively large bundles of filaments in short staple lengths) only rarely occur and the steel filaments are generally finely dispersed through the lengths of cotton.

Practice has shown that cotton fiber provides a better cushioning effect than polyester fiber perhaps for the reason that the surface friction characteristics of both cotton and the stainless steel filament used are similar. In any event, the juxtaposition of stainless steel and of cotton as shown, very effectively prevents slubbing and causes an even distribution of staple lengths of stainless steel filament throughout the yarn. It has been found that in general, the formation of slubs using the principles of the invention is minimal and that on the average only 200 small slubs may be found in any given sample of linear yards of grey goods. This is in comparison with goods made according to a prior process having about 1,300 much larger slubs in 100 linear yards of material. X-ray examination of grey goods produced by the presently disclosed process (FIG. 7) reveals that combinations of filaments where they occur average no more than four filaments per bundle (4-12 microns) and are invisible to the naked eye. FIG. 7 illustrates a typical distribution of steel filaments (greatly enlarged) in both weft and filling directions.

It will be understood that the foregoing description relates to a particular embodiment of the invention and is therefore representative. In order to appreciate the scope and spirit of the present invention, reference should be made to the appended claims.

What is claimed is:

1. An antistatic yarn comprising drawn staple length textile fibers and short staple lengths of metal filaments uniformly dispersed through the length of said yarn, said metal filaments being distributed throughout the length of said yarn so as to have an average density not greater than approximately four filaments at any crosssection along the length of said yarn.

' 2. The yarn according to claim I wherein said metal filaments are stainless steel in the 4 to 12 micron range.

3. The yarn according to claim 2 wherein the percentage of steel to fiber is approximately 0.5 percent to 1 percent by weight.

4. The yarn according to claim 3 wherein said fiber is a mixture of cotton fibers and polyester fibers.

5. A textile fabric made at least in part from yarns having antistatic properties comprising drawn staple length textile fibers, and short staple lengths of metal filaments uniformly dispersed through the length of said yarn, said metal filaments being distributed throughout the length of said yarn so as to have an average density not greater than approximately four filaments at any cross-section along the length of said yarn.

9. The textile fabric according to claim 8 wherein the fabric is made entirely of said antistatic yarn and said textile fibers of said yarn comprise a mixture of cotton fibers and polyester fibers. 

1. An antistatic yarn comprising drawn staple length textile fibers and short staple lengths of metal filaMents uniformly dispersed through the length of said yarn, said metal filaments being distributed throughout the length of said yarn so as to have an average density not greater than approximately four filaments at any cross-section along the length of said yarn.
 2. The yarn according to claim 1 wherein said metal filaments are stainless steel in the 4 to 12 micron range.
 3. The yarn according to claim 2 wherein the percentage of steel to fiber is approximately 0.5 percent to 1 percent by weight.
 4. The yarn according to claim 3 wherein said fiber is a mixture of cotton fibers and polyester fibers.
 5. A textile fabric made at least in part from yarns having antistatic properties comprising drawn staple length textile fibers, and short staple lengths of metal filaments uniformly dispersed through the length of said yarn, said metal filaments being distributed throughout the length of said yarn so as to have an average density not greater than approximately four filaments at any cross-section along the length of said yarn.
 6. A textile fabric according to claim 5 wherein said metal filaments are stainless steel in the 4 to 12 micron range.
 7. A textile fabric according to claim 6 wherein the percentage of steel fiber is approximately 0.5 percent to 1 percent by weight.
 8. A textile fabric according to claim 7 wherein said fiber is a mixture of cotton fibers and polyester fibers.
 9. The textile fabric according to claim 8 wherein the fabric is made entirely of said antistatic yarn and said textile fibers of said yarn comprise a mixture of cotton fibers and polyester fibers. 